Web pickup and transfer for a papermaking machine



arch 14, 1967 R. E. GROBE 3,309,263

WEB PICKUP AND TRANSFER FOR A PAPERMAKING MACHINE Filed Dec. 5, 1964' United States Patent 3,309,263 WEB PHIKUP AND TRANSFER FOR A PAPERMAKING MACHINE Ralph E. Grebe, Appleton, Wis., assignor to Kimberly- Clark Corporation, Neenah, Wis., a corporation of Delaware Filed Dec. 3, 1964, Ser. No. 415,654 2 Claims. ((11. 162306) The invention relates to Fourdrinier type papermaking machines in which a mixture of fibers and water is spread in an even layer upon the surface of a moving forming wire of fabric so that water drains from the mixture to form a moist web on the fabric and in which the moist web is transferred from the fabric to a felt that carries the web to a press section of the machine.

More particularly, the invention relates to an improved pickup device for picking up the moist web from the fabric and transferring it to the felt.

There are two principal conventional forms of pickup apparatus for transferring the moist web from a Fourdrinier wire to a felt. The more widely used one of these forms may be termed the solid pickup type which comprises a pickup roll nipped with a couch roll. The Fourdrinier wire is supported by a number of rolls including the couch roll; and the pickup roll, along with other rolls, support the felt whereby both the forming fabric and felt pass through the nip of the couch roll and pickup roll. In order to pick up the web from the wire and transfer it to the felt, pressure is necessary between the pickup and couch rolls of approximately 5 to 15 pounds per square inch. Utilizing such pressures, transfer of the moist web from the fabric to the felt is obtained by this arrangement, but the arrangement has drawbacks, one of which concerns the necessary crowning of the couch and pickup rolls. Without correct crowning, the sheet is crushed in this nip, either on the edges of the Web or in its center. The crowning thus must correspond to the pressures being used between the two rolls, since the rolls deflect somewhat with the nip pressure between them. Also, for acceptable results, the couch roll should have a drilled periphery to provide spaces in which water may migrate as the pickup and couch rolls squeeze the web in their nip, but due to the drilling, sheet marking may well occur, which, of course, is undesirable.

The other main form of conventional pickup apparatus may be termed the free wire pickup. This includes a pickup roll which is in contact with a free stretch of the Fourdrinier fabric extending between two spaced sup porting rolls. The pickup roll in this form of apparatus forms one of the supporting rolls for the felt loop. This type of apparatus, as compared to the solid type, advantageously does not require a drilled couch roll, and therefore marking of the sheet does not occur. However, the free wire pickup apparatus has a disadvantage in that the reach of forming fabric with which the pickup roll has a nip is unsupported directly opposite the pickup roll, and since the pickup roll must have a relatively large diameter of about 14 inches or more so that it does not bend excessively, it is not possible to obtain the nip pressures between the forming fabric and felt that are high enough to provide the thorough pickup of web obtained with the solid pickup.

It is an object of the present invention to provide an improved free wire pickup apparatus by means of which higher unit pressures between the felt and forming fabric are obtained, and in which a vacuum is applied on to the web, so that a higher proportion of the web is removed from the forming fabric to the felt than is possible with the conventional type of free wire pickup.

The invention consists of the novel constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above stated objects, and such other objects, as will be apparent from the following description of a preferred form of the invention, illustrated with reference to the accompanying drawing, wherein:;

FIG. 1 is a diagrammatic, side elevational view of a papermaking machine embodying the improved pickup device of the invention and showing also an end elevational view of the pickup device;

FIG. 2 is a side elevational view of the pickup device on an enlarged scale;

FIG. 3 is a sectional view taken on line 3-3 of FIG. 2 in the direction indicated; and,

FIG. 4 is a fragmentary view similar to FIG. 3 but on a still further enlarged scale.

Like characters of reference designate like parts in the several views.

Referring now to drawing, the papermaking machine which is fragmentarily illustrated, comprises an endless Fourdrinier wire or fabric 10 that is supported in the form of a loop by means of a plurality of rolls, the rolls including a couch roll 11 and a turning roll 12. At least one of the rolls which supports the fabric is driven so that the fabric moves about the rolls as indicated by the arrow 13. A conventional stock supply system and stock inlet (not shown) are used in connection with the wire 10 for depositing a mixture of water and fiber on to the wire so that the water drains through the openings in the wire and provides a paper web 14 on the wire which is substantially continuous but is quite wet when it reaches the turning roll 12.

The papermaking machine includes an endless pickup felt 15 held in looped form by supporting rolls, including rolls 16, 17 and 18. The pickup felt passes between the rolls 19 and 20 of a main press 21, and an endless bottom felt 22 supported by means of a plurality of supporting rolls (not shown) also passes through the nip between the rolls 19 and 20 along with the felt 15. The web 14 transfers from the fabric 10 on to the bottom surface of the felt 15 at a line of contact of the wire and felt and passes through the main press 21 to the conventional drier section of the machine (not shown).

The pickup felt 15 is forcefully held in contact with the wire 10 on a free stretch or run of the wire between the rolls 11 and 12 by means of a pickup cam 23 that bears on the felt 15. The cam 23 extends across the machine and is in contact with the felt 15 for its complete width. The cam 23 is supported by means of opposite journals 24 fitting in a suitable pair of side supports (not shown) that are fixed with respect to the machine frame, the cam 23 being rotatively fixed in substantially the position illustrated in FIG. 1. v

The pickup cam 23 comprises a hollow cylindrical member 25 close-d on its ends. A longitudinal slot 26 is provided in the cylindrical member 25, and a pair of angle members 27 and 28 are positioned in the slot. Member 27 includes the flanges 27a and 27b, and the member 28 includes flanges 28a and 28b. The flanges 27a and 28a extend through the slot 26 into the cylindrical member 25, and the flanges 27b and 28b lie parallel and in contact with the external surface of the cylindrical member 25.

A pair of lip members 29 and 30 lie in contact with the flanges 27b and 28b respectively, and these members and flanges are fixed together and with respect to the cylindrical member 25 by means of studs 31 and 32. The members 29 and 30 are provided with facing, thickened edge portions 29a and 30a forming a slot or passage 33 between them which is narrower than the slot 26 and is narrower than the distance between the flanges 27a and 28a. The increased thickness edge portions 2% and 30a form lips 29b and 30b, the external surfaces of which are curved and are on relatively small radii a and b. The lips 29b and 36b contact the felt 15 and hold it in forceful contact, along a line of contact, with the free stretch of the wire between the rolls 11 and 12.

A suction fitting 34 is connected to each end of the cylindrical member 25, and this fitting is connected to any suitable source of suction (not shown) so as to provide an evacuated condition within the cylindrical member 25. A water deflector 35 preferably is provided at the ends of the flanges 27a and 28a and extends coextensively with these flanges. The deflector 35 may be supported by means of support bars 36 that extend through the cylindrical member 25.

The radii a and b are preferably quite small so that the lips 29b and 3% apply a substantial unit pressure on to the felt 15. The radii a and b may, for example, be between inch and /2 inch. The slot 33 is quite narrow and may, for example, be A inch wide. I have found that when the felt is made to bear on a free run of the wire 10 with a narrow line of contact between felt and wire, greater unit pressures of the felt on the wire 16 may be obtained than are obtainable with a 14 inch pickup roll in a conventional free wire pickup, and a consequent more complete and better pickup of the web and transfer to the felt may be obtained, particularly with the cylindrical member 25 being evacuated so that vacuum is applied through the slot 33 onto the felt and thereby on the web that is in contact with the felt.

A number of different explanations may be advanced to explain the fact that more complete pickup of the web 14 is obtained using a narrow line of contact between the felt and wire. It is known that when using a 14 inch diameter pickup roll in a conventional free wire pickup arrangement, there is approximately a inch wide bead or band of water existing beneath the wire at the line of pickup. According to one explanation, this bead of water is sucked up into the felt by capillary action as the felt separates from the forming fabric substantially along the line of pickup and pulls the paper web along with the water. The suction exerted through the slot 33, of course, helps in drawing the water into the felt.

With the high unit pressures developed with the small radius lips 29b and 39b, more water is squeezed from the felt at the exact point of pickup, and there is a greater effect of the water in providing a complete transfer of the sheet to the felt, with the vacuum applied onto the felt through the slot 33 accentuating and increasing this effect. It may be mentioned by way of explanation that it is well recognized that with either the conventional solid pickup or the conventional free wire pickup, good sheet transfer is more easily obtained if a relatively wet paper web or a relatively wet felt is used. Experienced paper-making machine tenders, thus, usually add water to the pickup felt if trouble with pick up is had, making the pickup felt wetter. By utilizing my invention, this expedient need not be resorted to.

My improved free wire pickup apparatus provides the advantages above mentioned for free wire pickup as contrasted to solid pickup, such as lack of sheet marking; and, in addition, my improved apparatus provides irnproved sheet quality, less fiber losses and better appearance of the sheet. Also, less stream pollution results in view of the fact that a greater proportion of the fibers are taken from the forming fabric and transferred to the felt. Furthermore, there is less water consumption using the invention; and, in addition, the tension of the forming fabric 10 may be decreased to provide an increased fabric life while still obtaining a thorough pickup and transfer of the sheet to the felt.

I wish it to be understood that the invention is not to be limited to the specific constructions, arrangements and devices shown and described, except only insofar as the claims may be so limited, as it will be understood to those skilled in the art that changes may be made without departing from the principles of the invention.

What is claimed is:

1. In a papermaking machine, an endless perforate belt for draining a slurry of fibers and water deposited on the belt to form a moist paper web on the belt, a plurality of rolls for movably supporting the belt and including a pair of rolls providing an unsupported stretch of the belt between them, an endless felt, a plurality of rolls for movably supporting the felt, a guide member extending transversely across the felt holding the felt substantially in a line of contact with said unsupported stretch of said perforate belt, said guide member having a curved peripheral surface with a small radius in contact with the felt and being provided with a slot extending through said curved surface to be closed by the felt, and means for applying a suction onto said slot whereby the moist web is relatively cleanly picked up by the felt from the perforate belt and transfers at said line of contact to the felt.

2. In a papermaking machine, an endless perforate belt for draining a slurry of fibers and water deposited on the belt to form a moist paper web on the belt, a plurality of rolls for movably supporting the belt and including a pair of rolls providing an unsupported stretch of the belt between them, an endless felt, a plurality of rolls for movably supporting the felt, a hollow guide member extending transversely across the felt and having a longitudinal slot formed in it, a pair of lips which terminate along said slot and provide a slot between them which is in communication with said first mentioned slot and with the interior of said hollow member, said lips being in contact with the felt and holding the felt in a line of contact with said unsupported stretch of said perforate belt, said lips in their portions contacting the felt having relatively sharply curved edge surfaces of inch to /2 inch radius contacting the felt, and means for providing a vacuum within said hollow member so as to apply a vacuum to said slots and to the felt in contact with said lips whereby the moist web is relatively cleanly picked up by the felt from the perforate belt and transfers at said line of contact to said felt.

References Cited by the Examiner UNITED STATES PATENTS 1,586,358 5/1926 Eurich 162-279 FOREIGN PATENTS 889,244 2/ 1962 Great Britain.

DONALL H. SYLVESTER, Primary Examiner.

J. H. NEWSOME, Assistant Examiner. 

1. IN A PAPERMAKING MACHINE, AN ENDLESS PERFORATE BELT FOR DRAINING A SLURRY OF FIBERS AND WATER DEPOSITED ON THE BELT TO FORM A MOIST PAPER WEB ON THE BELT, A PLURALITY OF ROLLS FOR MOVABLY SUPPORTING THE BELT AND INCLUDING A PAIR OF ROLLS PROVIDING AN UNSUPPORTED STRETCH OF THE BELT BETWEEN THEM, AN ENDLESS FELT, A PLURALITY OF ROLLS FOR MOVABLY SUPPORTING THE FELT, A GUIDE MEMBER EXTENDING TRANSVERSELY ACROSS THE FELT HOLDING THE FELT SUBSTANTIALLY IN A LINE OF CONTACT WITH SAID UNSUPPORTED STRETCH OF SAID PERFORATE BELT, SAID GUIDE MEMBER HAVING A CURVED PERIPHERAL SURFACE WITH A SMALL RADIUS IN CONTACT WITH THE FELT AND BEING PROVIDED WITH A SLOT EXTENDING THROUGH SAID CURVED SURFACE TO BE CLOSED BY THE FELT, AND MEANS FOR APPLYING A SUCTION ONTO SAID SLOT WHEREBY THE MOIST WEB IS RELATIVELY CLEANLY PICKED UP BY THE FELT FROM THE 